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Sustainable Corn Production Supports Advanced Biofuel Feedstocks /
November 24, 2009 / News from the USDA Agricultural Research Service

It may be more cost-effective, energy-efficient
and environmentally sustainable to use corn stover for generating an
energy-rich oil called bio-oil and for making biochar to enrich soils and
sequester carbon than to turn it into cellulosic ethanol, according to a new
study from ARS. Photo courtesy of Courtesy of DOE/NREL.

Sustainable Corn Production Supports Advanced
Biofuel Feedstocks

Researchers worldwide are trying to economically convert cellulosic
biomass such as corn stover into "cellulosic ethanol." But
Agricultural Research Service (ARS)
scientists have found that it might be more cost-effective, energy-efficient
and environmentally sustainable to use corn stover for generating an
energy-rich oil called bio-oil and for making biochar to enrich soils and
sequester carbon.

Stover is made up of the leaves, husks, cobs and stalks of the corn
plant, and could provide an abundant source of feedstock for cellulosic ethanol
production after the grain is harvested. But removing stover from the field
would leave soil more vulnerable to erosion, deplete plant nutrients and
accelerate the loss of soil organic matter.

The team used fast pyrolysis, which is rapid heating in the absence of
oxygen, to transform corn stover and cobs into bio-oil and bio-char. They found
that the bio-oil captured 70 percent of the total energy input, and the energy
density of the bio-oil was five to 16 times the energy density of the
feedstock.

This suggests it could be more cost-effective to produce bio-oil
through a distributed network of small pyrolyzers and then transport the crude
bio-oil to central refining plants to make "green gasoline," rather than
transporting bulky stover to a large centralized cellulosic ethanol plant.

In addition, about 18 percent of the feedstock was converted into
bio-char, which contains most of the mineral nutrients in the corn residues.
Using biochar as a soil amendment would return those nutrients to the soil,
reduce leaching of other nutrients, help build soil organic matter and
sequester carbon. These benefits would help mitigate the adverse environmental
effects of harvesting stover for fuel production.